Pesticide benefits locust predators
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CTA. 1993. Pesticide benefits locust predators. Spore 48. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/49267
A pesticide that not only kills locusts, but simultaneously benefits one of their natural enemies, has been identified by scientists in South Africa. Normally pesticides kill both the target insects and their predators. But Roger Price and his...
A pesticide that not only kills locusts, but simultaneously benefits one of their natural enemies, has been identified by scientists in South Africa. Normally pesticides kill both the target insects and their predators. But Roger Price and his colleagues from the Plant Protection Research Institute in Pretoria, South Africa, made an interesting discovery when spraying brown locust nymphs (Locustna pardalina) with differing amounts of deltamethrin, a synthetic pyrethroid, to see if weather had any affect on the death rate of the insects. The researchers noticed that when they applied 15gm/ha of deltamethrin, the locusts sought shade in deep drifts under bushes. Two days later the heaps of locusts were seen crawling with maggots of the locust fly (Wolhlfahrtia pachytyli); the fly pupae were also present. The finding was surprising when doses of only 0.2am/ha of deltamethrin are used very effectively for tsetse control. Locusts take between three to five days to succumb to the pyrethroid, giving time for the predator fly to lay its eggs. Usually the fly invades locust nymphs while they are shedding their skins and are therefore relatively immobile. Active adult locusts are able to brush off the flies before they can lay their eggs and so under normal conditions only about 6% of locusts are parasitized. However, the level rose to an average of 30% parasitic control on those locusts suffering the effects of the deltamethrin. Researchers at the University of Witwatersrand are now studying W. pachytyli to determine how it copes with deltamethrin as this will have useful implications for locust control, if spraying at this dose rate is able to increase the parasitic presence in locust locations. Roger Price Plant Protection Research Institute Private Bag X116 Pretoria 0001 SOUTH AFRICA